In order to reduce the power consumption in mobile phones, and thus extend the battery time, the phone is often programmed to switch to a power saving mode such as to IDLE state or to the UTRAN Routing Area Paging Channel (URA-PCH) when there is no exchange of data with the network (e.g. in accordance with so called Fast Dormancy). Thus, when the Radio Link Control (RLC) buffer is empty, a timer starts running and, when it expires, the phone is switched to the IDLE state or the URA-PCH. An example of such a power saving mode is Fast Dormancy.
Switching the phone to URA-PCH instead of to IDLE state avoids some problems in the network signaling and also allows the phone to more quickly be brought back to the connected states CELL-FACH or CELL-DCH. However, since it normally takes much longer time for a user to prepare the content to send than for the phone to establish the connections to the network, the gain may not really be noticeable in practice. For a Mobile Terminated event, since the phone in URA-PCH is known to the network on the Routing Area (RA) level, the paging procedure, including reading the paging indicator and the following paging message, and then setting up the RRC connections, has to be performed on the same level. This can cause network access congestion, collision of the Random Access Signatures, missed detection or false alarm of the Acquisition Indications, and delays when many handsets in the same RA are to exchange important messages simultaneously. This in its turn can be damaging to business dependent on high frequency communications or a threat to life and properties in the occurrence of tsunami or the like while the warning system is still in its infancy.